Recently, organic semiconductor field-effect transistors (organic semiconductor field effect transistors (FETs)) operating with low power consumption have been researched and developed, and as an object for application thereof, radio frequency identification (RFID), for example, is drawing attention. Here, RFID reads and writes data in an RF tag on a noncontact basis using a radio wave. An RFID (RF tag) is desired to have an operating speed of approximately 20 to 100 kb/second according to a standard such as International Organization for Standardization (ISO) 14443, ISO 15693, or the like.
An RF tag to which a silicon semiconductor is applied, for example, reproduces (generates) a clock having a given frequency by receiving and frequency-dividing a signal of 13.56 MHz sent from a reader (reader-writer). For example, in ISO 15693, a clock of 26 kHz is generated by performing 1/512 frequency division of the carrier of 13.56 MHz from the reader, and in ISO 14443, a clock of 106 kHz is generated by performing 1/128 frequency division of the carrier of 13.56 MHz from the reader. Each clock is used as a clock having a symbol rate.
However, in an RF tag to which an organic semiconductor is applied, the operating frequency of an oscillator is, for example, on the order of hundreds of kHz, and it is difficult to generate a clock having a symbol rate by frequency-dividing the carrier of 13.56 MHz from the reader.
Incidentally, various proposals have been made with regard to clock recovery circuits (clock data recovery (CDR) circuits) applied to RF tags (RFID tags) or the like.